Currently, active matrix organic light emitting device (“AMOLED) displays are being proposed. The advantages of such displays include lower power consumption, manufacturing flexibility and faster refresh rate. In contrast to conventional LCD displays, there is no backlighting in an AMOLED display, and each pixel consists of different OLEDs, emitting light independently. The power consumed in each pixel has a relation with the magnitude of the generated light in that pixel. A typical pixel includes the organic light emitting device and a thin film drive transistor. A programming voltage is applied to the gate of the drive transistor which is roughly proportional to the current flowing through the drive transistor to the light emitting device. However, the use of current makes the performance of the pixel dependent on the drive transistor whose characteristics may change since many such transistors are currently fabricated from amorphous silicon. For example, the threshold voltage of amorphous silicon transistors may shift over long term use resulting in data from the programming voltage being incorrectly applied due to the shift.
While the active matrix organic light emitting diode (AMOLED) display is well-known for its low average power consumption, power consumption may still be higher than an active matrix liquid crystal display (AMLCD) at peak brightness. This makes an AMOLED display less appealing for applications such as emails, web surfing and eBooks due to the largely white (high brightness) background required to display such applications. The power dissipation in the AMOLED display is governed by that associated with the thin film drive transistor and the OLED itself. Although the development of a higher efficiency OLED continues to significantly lower the power consumption of the display, the power consumption of current OLED displays in applications requiring high brightness are greater than a comparable AMLCD. New approaches in TFT operation are therefore needed for further reduction in power. Thus a method to reduce power consumption to compensate for increased power requirements in certain brightness conditions is needed.